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authorJeremy Fitzhardinge <jeremy@goop.org>2007-05-02 19:27:16 +0200
committerAndi Kleen <andi@basil.nowhere.org>2007-05-02 19:27:16 +0200
commit7c3576d261ce046789a7db14f43303f8120910c7 (patch)
treead27a8459bbcdb183fe2411aec3b840942992ad5 /arch/i386/kernel/head.S
parent7a61d35d4b4056e7711031202da7605e052f4137 (diff)
[PATCH] i386: Convert PDA into the percpu section
Currently x86 (similar to x84-64) has a special per-cpu structure called "i386_pda" which can be easily and efficiently referenced via the %fs register. An ELF section is more flexible than a structure, allowing any piece of code to use this area. Indeed, such a section already exists: the per-cpu area. So this patch: (1) Removes the PDA and uses per-cpu variables for each current member. (2) Replaces the __KERNEL_PDA segment with __KERNEL_PERCPU. (3) Creates a per-cpu mirror of __per_cpu_offset called this_cpu_off, which can be used to calculate addresses for this CPU's variables. (4) Simplifies startup, because %fs doesn't need to be loaded with a special segment at early boot; it can be deferred until the first percpu area is allocated (or never for UP). The result is less code and one less x86-specific concept. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Signed-off-by: Andi Kleen <ak@suse.de> Cc: Andi Kleen <ak@suse.de>
Diffstat (limited to 'arch/i386/kernel/head.S')
-rw-r--r--arch/i386/kernel/head.S31
1 files changed, 6 insertions, 25 deletions
diff --git a/arch/i386/kernel/head.S b/arch/i386/kernel/head.S
index bb36c24311b4..12277d8938df 100644
--- a/arch/i386/kernel/head.S
+++ b/arch/i386/kernel/head.S
@@ -317,12 +317,12 @@ is386: movl $2,%ecx # set MP
movl %eax,%cr0
call check_x87
- call setup_pda
lgdt early_gdt_descr
lidt idt_descr
ljmp $(__KERNEL_CS),$1f
1: movl $(__KERNEL_DS),%eax # reload all the segment registers
movl %eax,%ss # after changing gdt.
+ movl %eax,%fs # gets reset once there's real percpu
movl $(__USER_DS),%eax # DS/ES contains default USER segment
movl %eax,%ds
@@ -332,16 +332,17 @@ is386: movl $2,%ecx # set MP
movl %eax,%gs
lldt %ax
- movl $(__KERNEL_PDA),%eax
- mov %eax,%fs
-
cld # gcc2 wants the direction flag cleared at all times
pushl $0 # fake return address for unwinder
#ifdef CONFIG_SMP
movb ready, %cl
movb $1, ready
cmpb $0,%cl # the first CPU calls start_kernel
- jne initialize_secondary # all other CPUs call initialize_secondary
+ je 1f
+ movl $(__KERNEL_PERCPU), %eax
+ movl %eax,%fs # set this cpu's percpu
+ jmp initialize_secondary # all other CPUs call initialize_secondary
+1:
#endif /* CONFIG_SMP */
jmp start_kernel
@@ -365,23 +366,6 @@ check_x87:
ret
/*
- * Point the GDT at this CPU's PDA. On boot this will be
- * cpu_gdt_table and boot_pda; for secondary CPUs, these will be
- * that CPU's GDT and PDA.
- */
-ENTRY(setup_pda)
- /* get the PDA pointer */
- movl start_pda, %eax
-
- /* slot the PDA address into the GDT */
- mov early_gdt_descr+2, %ecx
- mov %ax, (__KERNEL_PDA+0+2)(%ecx) /* base & 0x0000ffff */
- shr $16, %eax
- mov %al, (__KERNEL_PDA+4+0)(%ecx) /* base & 0x00ff0000 */
- mov %ah, (__KERNEL_PDA+4+3)(%ecx) /* base & 0xff000000 */
- ret
-
-/*
* setup_idt
*
* sets up a idt with 256 entries pointing to
@@ -553,9 +537,6 @@ ENTRY(empty_zero_page)
* This starts the data section.
*/
.data
-ENTRY(start_pda)
- .long boot_pda
-
ENTRY(stack_start)
.long init_thread_union+THREAD_SIZE
.long __BOOT_DS